Add The Ability to Specify Extra Volumes and Volume Mounts for Karmada Components

[jabellard]

What would you like to be added:
Today, when creating a Karmada instance to be managed by the Karmada operator, it's possible to specify extra args for the control plane components. However, it's not possible to specify extra volumes and volume mounts. This feature request is for providing the ability to specify extra volumes and volume mounts for the Karmada components.

Why is this needed:
At Bloomberg, we're currently building a managed Karmada platform and want to use the Karmada operator to manage the entire lifecycle of managed Karmada instances. We have tenants who have requirements such as the following:

• Ability to configure custom AuthN webhook
• Ability to configure encryption at rest

Given that it's already possible to specify extra args for components like the API server, having the ability to also specify extra volumes and volume mounts will enable those use cases.

[jabellard]

I just submitted a proposal for this.